1. Field of the Invention
The present invention relates to the field of projection type image display devices. More specifically, it relates to a projection type image display device having a rod integrator which equalizes illuminance of illumination light from a light source.
2. Background Arts
One of projection type image display devices known in the art is a projector which has an image generating section such as a liquid crystal element or a digital micromirror device (DMD) In this kind of projector, the image generating section modulates illumination light from a light source to an image light. Subsequently, the image light is projected on a screen through a projection optical system.
Because the illumination light from the light source might be uneven in illuminance, two Japanese patent laid-open publications No. 2003-16802 and No. 2003-59303 disclose a bar of rod integrator arranged between the light source and the image generating section. The rod integrator, for instance, is made of glass and it's one end along the axial direction is made into a light incident face while the other end is into a light exit face. The illumination light entered from the light incident face is equalized by reflecting on an inner surface of the rod integrator, then exits from the light exit face.
For using the space inside a housing effectively to downsize the projector, it would be better not to align the light source with the image generating section. Therefore, it is conventional to provide a mirror somewhere in between the light source and the image generating section to bend the light axis of the illumination light toward the image generating section.
A problem lies in the device described above that the number of components must be increased. The device also leads to the increased production cost because a component for precisely holding the mirror is required.